The invention relates to a multiple gear reversing transmission shiftable under load for construction machinery.
Those reversing transmissions are used in many different vehicles in the branch of construction machinery. Typical examples of use are in excavator loaders, fork lift trucks, wheel loaders, material handling machines and also mobile cranes. The multiplicity of vehicles in this field demands a great measure of adaptability of the transmission used, since the installation conditions in the different vehicles can turn up in the most varied ways.
The installation space available, for example, can turn out to be extremely small. Different center distances between the transmission input shaft and the transmission output shaft can also appear. Depending on the type of vehicle, a specific center distance is accordingly needed between the input and output shafts of the transmission. Besides, in most areas of use, at least one auxiliary drive is needed, for example, for the hydraulic system of the mobile machine. The functions that a reversing transmission has to perform are, therefore, very differently conditioned by the type of construction of the vehicle. The requirements must be met within the axial length and width of the transmission.
In EP 0 759 129 B1, a powershift reversing transmission was made known which, by virtue of the distribution of the gear clutches, fixed gears and idler gears among several countershafts, has an input gear set and a distributor gear set with which long and short center distances can be implemented. For long center distances, it is provided to situate the countershafts essentially between the input and the output shafts. Depending on the gear desired, different combinations of countershafts take part here in the transmission of power. In the case of short center distances, the countershafts are positioned in the circle around the input shaft whereby their position, relative to each other, is already predetermined. In the reversing transmission shaft arrangements different from each other are accordingly provided to implement different center distances.
The problem on which this invention is based is to provide a powershift multi-gear reversing transmission that is adaptable to different installation situations, that has a shaft arrangement adequate for bridging different center distances and that requires only a few additional parts in the adaptation to a certain installation situation.
The invention provides that the individual shafts of the reversing transmission be combined to form a transmission unit (KV, KR, K4) and a gear transmission unit (K1, K2, K3), the reversing transmission unit being provided in any side of the input shaft and the gear transmission unit being attached to the reversing transmission unit so that related to the input shaft the reversing transmission unit and the gear transmission unit is disposed in succession on one side of the input shaft.
The countershaft units can be comprised, for example, of a countershaft, a shifting device and idle and fixed gears. The reversing transmission unit consists of the countershaft unit for the forward gear, the reverse gear and the fourth gear. The gear transmission unit consists of the countershaft units for the first, the second and the third gear. The reversing transmission unit is preferably provided on any place of the periphery of the input shaft while the gear transmission unit is attached to the countershaft unit of the reverse gear.
In this manner, the shafts of the reversing transmission unit and the input shaft, the same as the shafts of the gear transmission unit and the shaft of the reverse gear, are respectively disposed to form a rectangle. The angles of the rectangle can be changed according to the momentary requirements of the specific installation situation.
By the shaft arrangement of the inventive shaft transmission, it is possible to implement both short and long center distances without it being needed to change the relative position to each other of the individual shafts. Only by variation of the distances between the individual shafts and of the angles formed by the connecting lines between two shafts is it possible to consider special standards of a certain vehicle type.
The flexible arrangement of the shafts can be attained without it being necessary to exchange the components that take part in the power flow. A maximum of possibilities for re-use of components is thus ensured.
According to a preferred embodiment of the invention, next to the input shaft, the reversing transmission has an auxiliary output such as a PTO. The installation of the PTO is made possible since, by virtue of the inventive arrangement of both transmission units on one side of the input shaft, there still is sufficient place for a PTO next to the input shaft. An engine-dependent auxiliary output is preferably used.
For vehicles that required from the transmission the bridging of still greater distances, a long distance variant can be provided such as can be implemented with a power divider transmission.
In another preferred embodiment of the invention, the countershaft unit of the fourth gear is placed next to the input shaft independently of the remaining countershaft units. The countershaft unit can also be eliminated from the reversing transmission when necessary. Such a construction is conceivable, for example, for forklift trucks which, as a rule, have only three different gears available. The space gained by the removal of the countershaft unit can be used for a second auxiliary output.
Accordingly, the instant invention makes it possible to consider the most different transmission requirements while retaining the basic transmission draft. Thereby material and costs can be spared and the transmission can be easily serviced. It is also possible to easily adapt an already existing transmission to new requirements.